Communication device and communication method

ABSTRACT

A communication device according to the disclosure includes: a signal generator that generates, on the basis of the first signal received from a communication partner through a coil, a second signal that synchronizes with the first signal; a first modulator configured to be able to modulate the first signal on the basis of the second signal; a second modulator configured to be able to modulate the first signal; and a communication controller that selects, on the basis of the first signal, whichever modulator is to be operated, from the first modulator and the second modulator.

TECHNICAL FIELD

The disclosure relates to a communication device utilized in short-rangewireless communication (NFC; Near Field Communication), and acommunication method utilized for the communication device.

BACKGROUND ART

Short-range wireless communication is a technique spreading mainly inthe Asian zone with regard to, for example, traffic systems, billing,and authentication, and is a technique ratified as an internationalstandard. A standard of the short-range wireless communication(hereinbelow also referred to as NFC standard) has compatibility, asso-called backward compatibility, with various standards such as TypeAstandard, TypeB standard, FeliCa standard, and ISO15693 standard. Inother words, for example, reader writers or cards in conformity with theNFC standard are also in conformity with all these standards.

In the short-range wireless communication, for example, the readerwriter transmits data to the card by ASK (Amplitude Shift Keying)modulation. The card transmits data to the reader writer by loadmodulation. For example, PTLs 1 and 2 disclose communication devicesthat are able to perform communication by the load modulation (passiveload modulation).

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No. 2013-62605

PTL 2: Japanese Unexamined Patent Application Publication No.2011-254156

SUMMARY OF THE INVENTION

Now, in general, in communication, higher communication quality isdesired, with expectation of further enhancement in communicationquality.

It is therefore desirable to provide a communication device and acommunication method that make it possible to enhance communicationquality.

A first communication device according to an embodiment of thedisclosure includes a signal generator, a first modulator, a secondmodulator, and a communication controller. The signal generatorgenerates, on the basis of a first signal received from a communicationpartner through a coil, a second signal that synchronizes with the firstsignal. The first modulator is configured to be able to modulate thefirst signal on the basis of the second signal. The second modulator isconfigured to be able to modulate the first signal. The communicationcontroller selects, on the basis of the first signal, whichevermodulator is to be operated, from the first modulator and the secondmodulator.

A second communication device according to an embodiment of thedisclosure includes a signal generator, a phase adjuster, and a firstmodulator. A coil receives a first signal from a communication partner.The signal generator generates, on the basis of a first signal receivedfrom a communication partner through a coil, a second signal thatsynchronizes with the first signal. The phase adjuster adjusts a phaseof the second signal on the basis of the first signal. The firstmodulator is configured to be able to modulate the first signal on thebasis of the second signal the phase of which has been adjusted by thephase adjuster.

A first communication method according to an embodiment of thedisclosure includes: allowing a coil to receive a first signal from acommunication partner; generating, on the basis of the first signal, asecond signal that synchronizes with the first signal; and selecting, onthe basis of the first signal, whichever modulator is to be operated,from a first modulator and a second modulator. The first modulator isconfigured to be able to modulate the first signal on the basis of thesecond signal, and the second modulator is configured to be able tomodulate the first signal.

A second communication method according to an embodiment of thedisclosure includes: allowing a coil to receive a first signal from acommunication partner; generating, on the basis of the first signal, asecond signal that synchronizes with the first signal; adjusting a phaseof the second signal on the basis of the first signal; and allowing afirst modulator to operate. The first modulator is configured to be ableto modulate the first signal on the basis of the second signal the phaseof which has been adjusted.

In the first communication device and the first communication methodaccording to the embodiments of the disclosure, the first modulator andthe second modulator are provided. The first modulator is configured tomodulate the first signal on the basis of the second signal thatsynchronizes with the first signal. Moreover, on the basis of the firstsignal, whichever modulator operates is selected from the firstmodulator and the second modulator.

In the second communication device and the second communication methodaccording to the embodiments of the disclosure, the first modulator isprovided. The first modulator is configured to modulate the first signalon the basis of the second signal that synchronizes with the firstsignal. The phase of the second signal is adjusted on the basis of thefirst signal.

According to the first communication device and the first communicationmethod of the embodiments of the disclosure, the first modulator and thesecond modulator are provided. On the basis of the first signal,whichever modulator is to be operated is selected from the firstmodulator and the second modulator. Hence, it is possible to enhance thecommunication quality.

According to the second communication device and the secondcommunication method of the embodiments of the disclosure, the firstmodulator is provided. The phase of the second signal is adjusted on thebasis of the first signal. Hence, it is possible to enhance thecommunication quality.

It is to be noted that effects of the disclosure are not necessarilylimited to the effects described above, and may include any of effectsthat are described herein.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is a block diagram that illustrates one configuration example ofa communication system according to a first embodiment of thedisclosure.

FIG. 2A is a waveform chart that illustrates one operation example of aphase synchronizer unit illustrated in FIG. 1.

FIG. 2B is a waveform chart that illustrates another operation exampleof the phase synchronizer unit illustrated in FIG. 1.

FIG. 3 is a schematic diagram provided for description of a concept ofactive load modulation.

FIG. 4 is a flowchart that illustrates one operation example of thecommunication system illustrated in FIG. 1.

FIG. 5 is a block diagram that illustrates one configuration example ofa communication system according to a modification example of the firstembodiment.

FIG. 6 is a flowchart that illustrates one operation example of thecommunication system illustrated in FIG. 5.

FIG. 7 is a block diagram that illustrates one configuration example ofa communication system according to a modification example of the firstembodiment.

FIG. 8 is a flowchart that illustrates one operation example of thecommunication system illustrated in FIG. 7.

FIG. 9 is a block diagram that illustrates one configuration example ofa communication system according to a second embodiment.

FIG. 10 is a characteristic diagram that illustrates one example ofcommunication characteristics by the active load modulation.

FIG. 11 is a flowchart that illustrates one operation example of thecommunication system illustrated in FIG. 9.

FIG. 12 is a flowchart that illustrates one operation example of acommunication system according to a modification example of the secondembodiment.

FIG. 13 is a block diagram that illustrates one configuration example ofa communication system according to a modification example of the secondembodiment.

FIG. 14 is a flowchart that illustrates one operation example of thecommunication system illustrated in FIG. 13.

FIG. 15 is a block diagram that illustrates one configuration example ofa communication system according to a modification example of the secondembodiment.

FIG. 16 is a flowchart that illustrates one operation example of thecommunication system illustrated in FIG. 15.

FIG. 17 is a block diagram that illustrates one configuration example ofa communication system according to a third embodiment.

FIG. 18 is a flowchart that illustrates one operation example of thecommunication system illustrated in FIG. 17.

MODES FOR CARRYING OUT THE INVENTION

In the following, some embodiments of the disclosure are described indetail with reference to the drawings. It is to be noted thatdescription is made in the following order.

1. First Embodiment 2. Second Embodiment 3. Third Embodiment 1. FirstEmbodiment Configuration Example

FIG. 1 illustrates one configuration example of a communication system 1including a communication device according to a first embodiment. Thecommunication system 1 performs communication by short-range wirelesscommunication. It is to be noted that since a communication methodaccording to an embodiment of the disclosure is embodied by thisembodiment, description thereof is made together. The communicationsystem 1 includes a communication device 10 and a communication device20.

The communication device 10 and the communication device 20 performcommunication with each other through a magnetic field. Specifically, inthe communication system 1, a coil 15 (described later) of thecommunication device 10 and a coil 21 (described later) of thecommunication device 20 form coupling through the magnetic field, totransmit or receive data by electromagnetic induction. At this occasion,the communication device 10 transmits, by ASK modulation, data to thecommunication device 20, and the communication device 20 transmits, bypassive load modulation or active load modulation, data to thecommunication device 10, as described latter. The communication device10 is applied to, for example, a reader writer, and is in conformitywith any one of various standards such as TypeA standard, TypeBstandard, FeliCa standard, and ISO15693 standard. The communicationdevice 20 is applied to, for example, a card, and is in conformity withNFC standard that has backward compatibility with these standards.

The communication device 10 includes a carrier signal generator unit 11,a data generator unit 12, a modulator unit 13, an amplifier 14, the coil15, a capacitor 16, and a demodulator unit 17.

The carrier signal generator unit 11 generates a carrier signal. Afrequency of the carrier signal is, for example, 13.56 MHz. The datagenerator unit 12 generates data D1 to be transmitted.

The modulator unit 13 modulates, by the ASK modulation, the carriersignal with the utilization of the data D1, to generate a signal S11.Moreover, the modulator unit 13 keeps from performing the ASKmodulation, in a case where the communication device 20 transmits dataD2 to the communication device 10.

The amplifier 14 generates a signal S12 on the basis of the signal S11,and outputs the signal S12 as an inter-terminal signal between a firstoutput terminal and a second output terminal. The first output terminalof the amplifier 14 is coupled to one end of the coil 15 and to one endof the capacitor 16. The second output terminal of the amplifier 14 iscoupled to another end of the coil 15 and to another end of thecapacitor 16.

The coil 15 generates the magnetic field on the basis of the signal S12,and forms coupling to the coil 21 (described later) of the communicationdevice 20 through the magnetic field. The one end of the coil 15 iscoupled to the first output terminal of the amplifier 14 and to the oneend of the capacitor 16, whereas the other end is coupled to the secondoutput terminal of the amplifier 14 and to the other end of thecapacitor 16. The one end of the capacitor 16 is coupled to the one endof the coil 15 and to the first output terminal of the amplifier 14,whereas the other end is coupled to the other end of the coil 15 and tothe second output terminal of the amplifier 14.

The demodulator unit 17 performs demodulating operation on the basis ofa voltage signal at the other end of the coil 15, to receive the data D2transmitted from the communication device 20. The demodulator unit 17 isconstituted by, for example, a so-called I/Q (In-phase/Quadrature)demodulator. In the communication system 1, the communication device 20performs communication by load modulation, in transmitting data to thecommunication device 10. Specifically, in a period when thecommunication device 10 transmits the carrier signal to thecommunication device 20, a communication controller unit 32 (describedlater) of the communication device 20 changes, in accordance with thedata. D2 to be transmitted, a load viewed from the communication device10. The change in the load appears, in the communication device 10, as,for example, a change in amplitude or a phase of the voltage signal atthe other end of the coil 15. The demodulator unit 17 detects theamplitude or the phase of the voltage signal at the other end of thecoil 15, to receive the data D2 transmitted from the communicationdevice 20. Moreover, the demodulator unit 17 supplies the data D2 toother blocks in the communication device 10.

It is to be noted that in this example, the demodulator unit 17 operateson the basis of the voltage signal at the other end of the coil 15, butthis is non-limiting. For example, the demodulator unit 17 may operateon the basis of a voltage signal at the one end of the coil 15, oralternatively, the demodulator unit 17 may operate on the basis of avoltage signal between both the ends of the coil 15.

The communication device 20 includes the coil 21, a capacitor 22,switches 23A and 23B, amplifiers 24A and 24B, a switch 25, a resistor26, a demodulator unit 27, a phase synchronizer unit 28, a phaseadjuster unit 29, an amplitude detector unit 30, a data generator unit31, and the communication controller unit 32.

The coil 21 forms coupling to the coil 15 of the communication device 10through the magnetic field, and generates, by the electromagneticinduction, a signal S21 corresponding to the signal S12 in thecommunication device 10. One end of the coil 21 is coupled to one end ofthe capacitor 22, to one end of the switch 23A, and to one end of theswitch 25. Another end of the coil 21 is coupled to another end of thecapacitor 22 and to one end of the switch 23B. The one end of capacitoris coupled to the one end of the coil 21, to the one end of the switch23A, and to the one end of the switch 25, whereas the other end iscoupled to the other end of the coil 21 and to the one end of the switch23B.

The one end of the switch 23A is coupled to the one end of the coil 21,to the one end of the capacitor 22, and to the one end of the switch 25,whereas another end is coupled to an output terminal of the amplifier24A. The one end of the switch 23B is coupled to the other end of thecoil 21 and to the other end of the capacitor 22, whereas another end iscoupled to an output terminal of the amplifier 24B. The switches 23A 23Bare turned on and off on the basis of a switch control signal SW1.

The amplifier 24A amplifies an output signal (a signal S23) of the phaseadjuster unit 29, and outputs the signal amplified. The amplifier 24Binverts and amplifies the output signal (the signal S23) of the phaseadjuster unit 29, and outputs the signal inverted and amplified.

With this configuration, in the communication device 20, as describedlater, turning on and off the switches 23A and 23B causes the activeload modulation to be performed.

The one end of the switch 25 is coupled to the one end of the coil 21,whereas another end is coupled to one end of the resistor 26. The switch25 is turned on and off, on the basis of a switch control signal SW2.The one end of the resistor 26 is coupled to the other end of the switch25, whereas another end is grounded. With this configuration, in thecommunication device 20, as described later, turning on and off theswitch 25 causes the passive load modulation to be performed.

The demodulator unit 27 performs the demodulating operation on the basisof a voltage signal at the other end of the coil 21, to receive the dataD1 transmitted from the communication device 10. The demodulator unit 27is constituted by an ASK demodulator. Moreover, the demodulator unit 27supplies the data D1 to other blocks in the communication device 20.

The phase synchronizer unit 28 generates, on the basis of the voltagesignal at the other end of the coil 21, a signal S22 that synchronizeswith the voltage signal. The phase synchronizer unit 28 is constitutedwith the utilization of a PLL (Phase Locked Loop).

FIGS. 2A and 2B illustrate one operation example of the phasesynchronizer unit 28. FIG. 2A illustrates operation in a case where acommunication distance from the communication device 10 to thecommunication device 20 is short. FIG. 2B illustrates operation in acase where the communication distance is long. In the case with theshort communication distance, a coupling coefficient of the coil 15 ofthe communication device 10 and the coil 21 of the communication device20 becomes large, causing an increase in amplitude of the signal S21.Meanwhile, in the case with the long communication distance, thecoupling coefficient of the coil 15 and the coil 21 becomes small,causing a decrease in the amplitude of the signal S21. The phasesynchronizer unit 28 generates, regardless of the amplitude of thesignal S21, on the basis of the voltage signal at the other end of thecoil 21, the signal S22 that synchronizes with the voltage signal.

The phase adjuster unit 29 adjusts a phase of the signal S22 by anamount of a phase shift in accordance with an instruction from thecommunication controller unit 32, and outputs, as the signal S23, asignal whose phase has been adjusted. The phase adjuster unit 29 may beconstituted with the utilization of, for example, a variable delaycircuit. It is to be noted that this is non-limiting, but the phaseadjuster unit 29 may be constituted by anything that is able to makephase adjustments.

The amplitude detector unit 30 detects, on the basis of the voltagesignal at the other end of the coil 21, an amplitude value V_(SW) of thevoltage signal. As described above, because the amplitude of the signalS21 changes with the communication distance from the communicationdevice 10 to the communication device 20, the amplitude of the voltagesignal at the other end of the coil 21 also changes in a similar mannerin accordance with the communication distance. Accordingly, theamplitude detector unit 30 detects the amplitude value V_(SW) of thevoltage signal, and supplies a detection result to the communicationcontroller unit 32.

It is to be noted that in this example, the demodulator unit 27, thephase synchronizer unit 28, and the amplitude detector unit 30 operateon the basis of the voltage signal at the other end of the coil 21, butthis is non-limiting. For example, the demodulator unit 27, the phasesynchronizer unit 28, and the amplitude detector unit 30 may operate onthe basis of a voltage signal at the one end of the coil 21, oralternatively, the demodulator unit 27, the phase synchronizer unit 25,and the amplitude detector unit 30 may operate on the basis of a voltagesignal between both the ends of the coil 21.

The data generator 31 generates the data D2 to be transmitted, andsupplies the data D2 to the communication controller unit 32.

The communication controller unit 32 generates the switch controlsignals SW1 and SW2 on the basis of the amplitude value V_(SW) and onthe basis of the data D2. The communication controller unit 32 suppliesthe switch control signal SW1 to the switches 23A and 23B, whilesupplying the switch control signal SW2 to the switch 25. Specifically,the communication controller unit 32 turns on and off the switch 25 inaccordance with the data D2, in a case where the amplitude value V_(SW)is equal to or larger than a predetermine threshold value Vth1. In otherwords, in this case, the communication device 20 utilizes the passiveload modulation, in transmitting the data D2. Moreover, thecommunication controller unit 32 turns on and off the switches 23A and23B in accordance with the data D2, in a case where the amplitude valueis smaller than the predetermine threshold value Vth1. In other words,in this case, the communication device 20 utilizes the active loadmodulation, in transmitting the data D2.

Furthermore, the communication controller unit 32 has a function ofsetting the amount of the phase shift in the phase adjuster unit 29.Hence, in the communication device 20, as described later, it ispossible to increase the communication distance, in transmitting thedata D2 to the communication device 10 by the active load modulation.

Here, the communication device 20 corresponds to one specific example ofa “communication device” in the disclosure. The phase synchronizer unit28 corresponds to one specific example of a “signal generator” in thedisclosure. The amplifiers 24A and 24B, and the switches 23A and 23Bcorrespond to one specific example of a “first modulator” in thedisclosure. The switch 25 corresponds to one specific example of a“second modulator” in the disclosure. The amplitude detector unit 30 andthe communication controller unit 32 correspond to one specific exampleof a “communication controller” in the disclosure.

[Operation and Workings]

Description is given next of operation and workings of the communicationsystem 1 according to this embodiment.

[Outline of Overall Operation]

First, an outline of overall operation of the communication system 1 isdescribed with reference to FIG. 1.

The communication device 10 transmits, by the ASK modulation, the dataD1 to the communication device 20. Specifically, first, in thecommunication device 10, the carrier signal generator unit 11 generatesthe carrier signal, and the data generator unit 12 generates the data D1to be transmitted. The modulator unit 13 modulates, by the ASKmodulation, the carrier signal with the utilization of the data D1, togenerate the signal S11. The amplifier 14 generates the signal S12 onthe basis of the signal S11. The coil 15 generates the magnetic field onthe basis of the signal S12. In the communication device 20, the coil 21generates the signal S21 on the basis of the magnetic field generated bythe coil 15. The demodulator unit 27 performs the demodulating operationon the basis of the voltage signal at the other end of the coil 21, toreceive the data D1 transmitted from the communication device 10.

The communication device 20 transmits, by the load modulation, the dataD2 to the communication device 10. Specifically, first, in the periodwhen the communication device 10 transmits the carrier signal to thecommunication device 20, the amplitude detector unit 30 detects theamplitude value V_(SW) of the voltage signal at the other end of thecoil 21. The phase synchronizer unit 28 generates, on the basis of thevoltage signal at the other end of the coil 21, the signal S22 thatsynchronizes with the voltage signal. The phase adjuster unit 29 adjuststhe phase of the signal S22 by the amount of the phase shift inaccordance with the instruction from the communication controller unit32, and outputs, as the signal S23, the signal whose phase has beenadjusted. The communication controller unit 32 generates the switchcontrol signals SW1 and SW2 on the basis of the amplitude value V_(SW)and on the basis of the data D2. The communication controller unit 32supplies the switch control signal SW1 to the switches 23A and 23B,while supplying the switch control signal SW2 to the switch 25. Thus,the load viewed from the communication device 10 changes in accordancewith the data D2. The demodulator unit 17 of the communication device 10performs the demodulating operation on the basis of the voltage signalat the other end of the coil 15, to receive the data D2 transmitted fromthe communication device 20.

[Regarding Load Modulation]

The communication device 20 transmits, by the load modulation, the dataD2 to the communication device 10. At this occasion, the communicationcontroller unit 32 selects, on the basis of the amplitude value V_(SW),either the passive load modulation or the active load modulation.

In the passive load modulation, in the period when the communicationdevice 10 transmits the carrier signal to the communication device 20,the communication controller unit 32 turns on and off the switch 25 inaccordance with the data D2 Upon the switch 25 being turned on, the oneend of the coil 21 is grounded through the resistor 26. This causes theload viewed from the communication device 10 to change in accordancewith the data D2. The demodulator unit 17 of the communication device 10performs the demodulating operation on the basis of the change in theload, to receive the data. D2 transmitted from the communication device20.

In the active load modulation, in the period when the communicationdevice 10 transmits the carrier signal to the communication device 20,the communication controller unit 32 turns on and off the switches 23Aand 23B in accordance with the data D2. Upon the switches 23A and 23Bbeing turned on, the output signal of the amplifier 24A is supplied tothe one end of the coil 21, while the output signal of the amplifier 24Bis supplied to the other end of the coil 21. In other words, a signalthat synchronizes with the carrier signal is supplied to between boththe ends of the coil 21. This causes the coil 21 to generate themagnetic field. Thus, in the active load modulation, unlike the passiveload modulation, the coil 21 is directly supplied with the signal W2that synchronizes with the carrier signal, causing the magnetic field tochange significantly. This causes the load viewed, from thecommunication device 10 to change in accordance with the data D2. On thebasis of the change in the load, the demodulator unit 17 of thecommunication device 10 performs the demodulating operation, to receivethe data D2 transmitted from the communication device 20.

FIG. 3 schematically illustrates operation of the active loadmodulation. The coil 15 of the communication device 10 generates themagnetic field on the basis of the carrier signal W1. The coil 21 of thecommunication device 20 generates the magnetic field on the basis of thesignal W2 that synchronizes with the carrier signal, in a period whenthe switches 23A and 23B are turned on. Moreover, the demodulator unit17 of the communication device 10 performs the demodulating operation onthe basis of a composite signal W3 of the carrier signal W1 and thesignal W2. The composite signal W3 may be represented as follows.

[Expression 1]

A sin(ωt)+B sin(ωt+θ)=√{square root over (A ² +B ²+2AB cos θ)}sin(θ+φ)  (1)

Here, a first term of a left side denotes the carrier signal W1. Asecond term of the left side denotes the signal W2. Thus, the compositesignal W3 may be represented with the utilization of a composite theoremof a sine wave. Adjusting the amount of the phase shift in the phaseadjuster unit 29 of the communication device 20 makes it possible toadjust a phase θ in the expression (1). Hence, in the active loadmodulation, it is possible to increase amplitude of the composite signalW3, leading to an increase in a degree of modulation. As described, inthe communication system 1, setting the amount of the phase shift in thephase adjuster unit 29 at an appropriate value makes it possible toincrease the communication distance from the communication device 10 tothe communication device 20.

[Detailed Operation]

FIG. 4 illustrates one operation example of the communication system 1.In the communication system 1, first, the communication device 10transmits the data D1 to the communication device 20. Moreover, thecommunication device 20 transmits the data D2 to the communicationdevice 10, to make a response. In the following, this operation isdescribed in detail.

First, the communication device 10 transmits, by the ASK modulation, thedata D1 to the communication device 20 (step S1).

Thereafter, the demodulator unit 27 of the communication device 20 makesa confirmation as to whether or not the demodulator unit 27 has receivedthe data D1 (step S2). In a case where the demodulator unit 27 hasreceived the data D1, the data generator unit 31 of the communicationdevice 20 generates the data D2 for the response to the communicationdevice 10, and the flow proceeds to step S3. Moreover, in a case wherethe demodulator unit 27 has failed in receiving the data D1, the flowreturns to step S1, and repeats the steps S1 and S2 until reception.

Thereafter, the amplitude detector unit 30 of the communication device20 detects the amplitude value V_(SW) of the voltage signal at the otherend of the coil 21 (step S3).

Thereafter, the communication controller unit 32 of the communicationdevice 20 compares the amplitude value V_(SW) detected in step S3 withthe predetermined threshold value Vth1 (step S4). In a case where theamplitude value V_(SW) is equal to or larger than the threshold valueVth1 (V_(SW)≧Vth1), the communication device 20 transmits, by thepassive load modulation, the data D2 to the communication device 10(step S5). Specifically, the communication controller unit 32 turns onand off the switch 25 with the utilization of the switch control signalSW2, in accordance with the data D2. In other words, in the case wherethe amplitude value V_(SW) is equal to or larger than the thresholdvalue Vth1, the communication controller unit 32 determines that thecommunication distance from the communication device 10 to thecommunication device 20 is short, and selects the passive loadmodulation.

Meanwhile, in step S4, in a case where the amplitude value V_(SW) issmaller than the threshold value Vth1 (V_(SW)<Vth1), the communicationdevice 20 transmits, by the passive load modulation, the data D2 to thecommunication device 10 (step S6). Specifically, the communicationcontroller unit 32 turns on and off the switches 23A and 23B with theutilization of the switch control signal SW1, in accordance with thedata D2, in other words, in the case where the amplitude value V_(SW) issmaller than the threshold value Vth1, the communication controller unit32 determines that the communication distance from the communicationdevice 10 to the communication device 20 is long, and selects the activeload modulation.

Thus, the flow ends.

As described, in the communication system 1, a configuration is made tobe able to select either the passive load modulation or the active loadmodulation. Hence, it is possible to enhance communication quality.

Specifically, in the communication device 20, in the case where theamplitude value V_(SW) is equal to or larger than the threshold valueVth1, the determination is made that the communication distance from thecommunication device 10 to the communication device 20 is short. Thus,the passive load modulation is selected. In other words, in the casewith the short communication distance, there is no necessity of usingthe active load modulation that allows for the increase in thecommunication distance. Accordingly, the passive load modulation isselected. Hence, in the communication system 1, it is possible to reducepossibility of occurrence of erroneous operation. In other words, forexample, in a case where the active load modulation is utilized with thecommunication distance being short, the magnetic field becomes toostrong, contributing to the possibility of the occurrence of theerroneous operation in the communication device 10. In contrast, in thecommunication system 1, the passive load modulation is utilized in thecase with the short communication distance. This makes it possible torestrain the strength of the magnetic field, leading to reduction in thepossibility of the occurrence of the erroneous operation. As a result,in the communication system 1, it is possible to enhance thecommunication quality in the case with the short communication distance.

Moreover, in the communication device 20, in the case where theamplitude value V_(SW) is smaller than the threshold value Vth1, thedetermination is made that the communication distance from thecommunication device 10 to the communication device 20 is long. Thus,the active load modulation is selected. This makes it possible toperform communication even in a case where the communication device 10and the communication device 20 are spaced away. As a result, in thecommunication system 1, it is possible to enhance the communicationquality in the case with the long communication distance.

[Effects]

As described, in this embodiment, the configuration is made to be ableto select either the passive load modulation or the active loadmodulation. Hence, it is possible to enhance the communication quality.

Modification Example 1

In the forgoing embodiment, either the passive load modulation or theactive load modulation is selected on the basis of the amplitude valueV_(SW), but this is non-limiting. In the following, this modificationexample is described in detail by giving some examples.

FIG. 5 illustrates one configuration example of a communication system1B according to this modification example. The communication system 13includes a communication device 20B. The communication device 20Bincludes a demodulator unit 27B and a communication controller unit 32B.

The demodulator unit 27B performs the demodulating operation on thebasis of the voltage signal at the other end of the coil 21, to receivethe data D1 transmitted from the communication device 10, as with thedemodulator unit 27 according to the forgoing embodiment. Moreover, thedemodulator unit 27B distinguishes a standard with which thecommunication device 10 is in conformity (a communication standard SP),and supplies a distinction result to the communication controller unit32. An example of distinction methods may be to utilize the degree ofthe modulation of a signal transmitted from the communication device 10.In other words, as described above, the communication device 10 is inconformity with any one of the various standards such as the TvpeAstandard, the TypeB standard, the FeliCa standard, and the ISO15693standard. The modulator unit 13 of the communication device 10 performsthe ASK modulation at the degree of the modulation corresponding to thestandard with which the communication device 10 is in conformity.Accordingly, the demodulator unit 27B is able to distinguish, on thebasis of the degree of the modulation of the signal transmitted from thecommunication device 10, the standard with which the communicationdevice 10 is in conformity (the communication standard SP). It is to benoted that this is non-limiting. The demodulator unit 27B maydistinguish the communication standard SP on the basis of, for example,other features of the signal (coding, a bit rate, and/or a sub carrier).Moreover, in a case where information in accordance with thecommunication standard SP is included in the data D1 transmitted by thecommunication device 10, the demodulator unit 27B may distinguish thecommunication standard SP on the basis of the information.

The communication controller unit 32B generates the switch controlsignals SW1 and SW2 on the basis of the communication standard SP and onthe basis of the data D2. Specifically, the communication controllerunit 32B turns on and off the switches 23A and 23B in accordance withthe data D2, in a case where the communication standard SP is includedin one or more communication standards set in advance. In other words,in this case, the communication device 20B utilizes the active loadmodulation. Here, the one or more communication standards set in advanceare, for example, standards utilized in applications with the longcommunication distances, and may include, for example, the FeliCastandard. Moreover, the communication controller unit 32B turns on andoff the switch 25 in accordance with the data D2, in a case where thecommunication standard SP is not included in the one or morecommunication standards, in other words, in this case, the communicationdevice 20B utilizes the passive load modulation.

Here, the demodulator unit 27B and the communication controller unit 32Bcorrespond to one specific example of the “communication controller” inthe disclosure.

FIG. 6 illustrates one operation example of the communication system 19.

First, as with the case of the communication system 1 (FIG. 4), thecommunication device 10 transmits, by the ASK modulation, the data D1 tothe communication device 20B (step S1). The demodulator unit 27B of thecommunication device 20B makes the confirmation as to whether or not thedemodulator unit 27B has received the data D1 (step S2).

Thereafter, the demodulator unit 27B of the communication device 20Bdistinguishes the communication standard SP (step S13).

Thereafter, the communication controller unit 32B of the communicationdevice 20B makes a confirmation as to whether or not the communicationstandard SP distinguished in step S13 is included in the one or morepredetermined communication standards set in advance (step S14). In acase where the communication standard SP is included in the one or morepredetermined communication standards, the communication device 20Btransmits, by the active load modulation, the data D2 to thecommunication device 10 (step S15). Meanwhile, in a case where thecommunication standard SP is not included in the one or morepredetermined communication standards, the communication device 20Btransmits, by the passive load modulation, the data D2 to thecommunication device 10 (step S16).

Thus, the flow ends.

As described, in the communication system 1B, the active load modulationis selected in the case where the communication standard SP is includedin the one or more predetermined communication standards that areutilized in the applications with the long communication distances. Thepassive load modulation is selected in the case where the communicationstandard SP is not included in the one or more predeterminedcommunication standards. Hence, it is possible to enhance thecommunication quality.

FIG. 7 illustrates one configuration example of another communicationsystem 1C according to this modification example. The communicationsystem 1C includes a communication device 20C. The communication device20C includes the demodulator unit 27B and a communication controllerunit 32C. The communication controller unit 32C generates the switchcontrol signals SW1 and SW2 on the basis of the amplitude value V_(SW),the communication standard SP, and the data D2. Specifically, first, thecommunication controller unit 32C sets the predetermined threshold valueVth1 on the basis of the communication standard SP. The threshold valueVth1 is set at a larger value, as the communication distance for thecommunication standard SP is shorter. For example, because the TypeBstandard is a standard that involves performing communication at ashorter distance than those of the TypeA standard and the FeliCastandard, the threshold value Vth1 is set at a large value. Moreover,the communication controller unit 32C turns on and off the switch 25 inaccordance with the data D2, in the case where the amplitude valueV_(SW) is equal to or larger than the predetermined threshold valueVth1. In other words, in this case, the communication device 20Cutilizes the passive load modulation. Meanwhile, the communicationcontroller unit 32C turns on and off the switches 23A and 23B inaccordance with the data D2, in the case where the amplitude valueV_(SW) is smaller than the predetermined threshold value Vth1. In otherwords, in this case, the communication controller unit 32C utilizes theactive load modulation.

Here, the amplitude detector unit 30, the demodulator 27B, and thecommunication controller unit 32C correspond to one specific example ofthe “communication controller” in the disclosure.

FIG. 8 illustrates one operation example of the communication system 1C.

First, as with the case of the communication system 1B (FIG. 6), thecommunication device 10 transmits, by the ASK modulation, the data D1 tothe communication device 20 (step S1). The demodulator unit 27B of thecommunication device 20C makes the confirmation as to whether or not thedemodulator unit 27B has received the data D1 (step S2).

Thereafter, the demodulator unit 27B of the communication device 20Cdistinguishes the communication standard SP (step S13).

Thereafter, the communication controller unit 32C of the communicationdevice 20C sets the threshold value Vth1 on the basis of thecommunication standard SP distinguished in step S13 (step S24).

Thereafter, the amplitude detector unit 30 of the communication device20C detects the amplitude value V_(SW) of the voltage signal at theother end of the coil 21 (step S3).

Thereafter, the communication controller unit 32C of the communicationdevice 20C compares the amplitude value V_(SW) detected in step S3 withthe predetermined threshold value Vth1 (step S4). In the case where theamplitude value V_(SW) is equal to or larger than the threshold valueVth1 (V_(SW)≧Vth1), the communication device 20 transmits, by thepassive load modulation, the data D2 to the communication device 10(step S5). Meanwhile, in the case where the amplitude value V_(SW) issmaller than the threshold value Vth1 (V_(SW)<Vth1), the communicationdevice 20 transmits, by the passive load modulation, the data D2 to thecommunication device 10 (step S6).

Thus, the flow ends.

As described, in the communication system 1C, the threshold value Vth1is set on the basis of the communication standard SP. Hence, it ispossible to enhance the communication quality. In other words, thestandards such as the TypeA standard, the TypeB standard, the FeliCastandard, and the ISO15693 standard differ in communication performancefrom one another, and therefore differ in upper limits of thecommunication distances that allow for communication by the passive loadmodulation. Specifically, for example, because the TypeB standard is astandard for the short communication distance, it is necessary to setthe threshold value Vth1 at a larger value than those of the TypeAstandard and the FeliCa standard. Thus, the active load modulation ismore likely to be selected in the TypeB standard, leading to theincrease in the communication distance. As described above, in thecommunication system 1C, utilizing the threshold value Vth1 inaccordance with the communication standard SP makes it possible to makea change-over between the passive load modulation and the active loadmodulation, in accordance with the communication performance in therelevant communication standard. SP. As a result, in the communicationsystem 1C, it is possible to enhance the communication quality.

2. Second Embodiment

Description is given next of a communication system 2 according to asecond embodiment. This embodiment includes transmitting data by theactive load modulation, without utilizing the passive load modulation.It is to be noted that substantially same constituent parts as those ofthe communication system 1 according to the forgoing first embodimentare denoted by the same reference characters, and description thereof isomitted as appropriate.

FIG. 9 illustrates one configuration example of the communication system2 according to this embodiment. The communication system 2 includes acommunication device 40. The communication device 40 includes the coil21, the capacitor 22, the switches 23A and 23B, the amplifiers 24A and24B, the demodulator unit 27, the phase synchronizer unit 28, the phaseadjuster unit 29, the amplitude detector unit 30, the data generatorunit 31, and a communication controller unit 42. In other words, thecommunication device 40 is an equivalent of the communication device 20according to the first embodiment, except that the switch 25 and theresistor 26 are eliminated, and that the communication controller unit32 is replaced with the communication controller unit 42. That is, thecommunication device 40 transmits the data D2 to the communicationdevice 10, by the active load modulation, without utilizing the passiveload modulation.

The communication controller unit 42 generates the switch control signalSW1 on the basis of the data D2, and supplies the switch control signalSW1 to the switches 23A and 23B. Moreover, the communication controllerunit 42 also has the function of setting the amount of the phase shiftin the phase adjuster unit 29, on the basis of the amplitude valueV_(SW). Hence, as described below, it is possible to increase thecommunication distance.

In other words, first, the phase synchronizer unit 28 disposed at apre-stage of the phase adjuster unit 29 generates, on the basis of thevoltage signal at the other end of the coil 21, the signal S22 thatsynchronizes with the voltage signal. At this occasion, in some cases,the phase of the output signal S22 of the phase synchronizer unit 28changes in accordance with the amplitude value V_(SW) of the voltagesignal at the other end of the coil 21. In this case, as represented bythe expression (1), the amplitude in the composite signal W3 changes,causing possibility of a change in an upper limit of a communicationdistance from the communication device 10 to the communication device 40(a communication-enabling distance).

FIG. 10 illustrates the communication-enabling distance in the TypeBstandard. In FIG. 10, a vertical axis denotes the communication-enablingdistance, whereas a horizontal axis denotes a phase of the signal S23,with reference to the phase of the voltage signal at the other end ofthe coil 21.

As illustrated in FIG. 10, as the phase of the signal S23 changes, thecommunication-enabling distance changes. In other words, as representedby the expression (1), as the phase of the signal S23 changes, theamplitude in the composite signal W3 changes, causing the degree of themodulation to change. As a result, the communication-enabling distancechanges. In this example, in a case where the amplitude value V_(SW) is0.54V, the communication-enabling distance becomes the smallest in acase where the phase of the signal S23 is at or around 30 degrees.Likewise, in a case where the amplitude value V_(SW) is 1.32V, thecommunication-enabling distance becomes the smallest in a case where thephase of the signal S23 is at or around 60 degrees.

The communication controller unit 42 sets, on the basis of the amplitudevalue V_(SW), the amount of the phase shift in the phase adjuster unit29, to increase the communication-enabling distance. Specifically, thecommunication controller unit 42 sets the amount of the phase shift inthe phase adjuster unit 29 at an amount of a phase shift P1, in a casewhere the amplitude value V_(SW) is equal to or larger than apredetermined threshold Vth2. The amount of the phase shift P1 is so setas to increase the communication-enabling distance, in a case where theamplitude value V_(SW) is large. Moreover, the communication controllerunit 42 sets the amount of the phase shift in the phase adjuster unit 29at an amount of a phase shift P2, in a case where the amplitude valueV_(SW) is smaller than the predetermined threshold Vth2. The amount ofthe phase shift P2 is so set as to increase the communication-enablingdistance, in a case where the amplitude value V_(SW) is small. Hence, inthe communication system 2, it is possible to increase the communicationdistance.

Here, the communication device 40 corresponds to one specific example ofthe “communication device” in the disclosure. The phase adjuster unit29, the amplitude detector unit 30, and the communication controllerunit 42 correspond to one specific example of a “phase adjuster” in thedisclosure.

FIG. 11 illustrates one operation example of the communication system 2.

First, as with the case of the communication system 1 according to thefirst embodiment (FIG. 4), the communication device 10 transmits, by theASK modulation, the data D1 to the communication device 40 (step S1).The demodulator unit 27 of the communication device 40 makes theconfirmation as to whether or not the demodulator unit 27 has receivedthe data D1 (step S2).

Thereafter, the amplitude detector unit 30 of the communication device40 detects the amplitude value V_(SW) of the voltage signal at the otherend of the coil 21 (step S3).

Thereafter, the communication controller unit 42 of the communicationdevice 40 compares the amplitude value V_(SW) detected in step S3 withthe predetermine threshold value Vth2 (step S34). In a case where theamplitude value V_(SW) is equal to or larger than the threshold valueVth2 (V_(SW)≧Vth2), the communication controller unit 42 sets the amountof the phase shift in the phase adjuster unit 29 at the amount of thephase shift P1 (step S35). Meanwhile, in a case where the amplitudevalue V_(SW) is smaller than the threshold value Vth2 (V_(SW)<Vth2), thecommunication controller unit 42 sets the amount of the phase shift inthe phase adjuster unit 29 at the amount of the phase shift P2 (stepS36).

Thereafter, the communication device 40 transmits, by the active loadmodulation, the data D2 to the communication device 10 (step S37).

Thus, the flow ends.

As described, in the communication system 2, the amount of the phaseshift in the phase adjuster unit 29 is adjusted. Hence, it is possibleto increase the communication distance, in particular, in thecommunication system 2, the amount of the phase shift in the phaseadjuster unit 29 is adjusted on the basis of the amplitude value V_(SW).Accordingly, even in a case where the phase of the output signal S22 ofthe phase synchronizer unit 28 changes in accordance with the amplitudevalue V_(SW), it is possible to restrain the communication distance frombeing affected by the change in the phase. As a result, in thecommunication system 2, it is possible to enhance the communicationquality.

As described above, in this embodiment, a configuration is made to beable to adjust the amount of the phase shift in the phase adjuster unit.Hence, it is possible to enhance the communication quality.

Modification Example 2-1

In the forgoing embodiment, the amplitude value V_(SW) is compared withthe single threshold value Vth2, to set the amount of the phase shift inthe phase adjuster unit 29. However, this is non-limiting. In onealternative, for example, a plurality of threshold values may beprovided. The amplitude value V_(SW) may be compared with the pluralityof the threshold values, to set the amount of the phase shift in thephase adjuster unit 29 more finely. Moreover, for example, asillustrated in FIG. 12, a look-up table may be utilized that summarizesrelation between the amplitude value V_(SW) and the amount of the phaseshift in the phase adjuster unit 29. A communication controller unit 42Aaccording to this modification example sets, in step S44, the amount ofthe phase shift in the phase adjuster unit 29, on the basis of theamplitude value V_(SW) detected in step S3, with the utilization of thelook-up table. It is to be noted that the look-up table is utilized inthis example, but this is non-limiting. A function may be utilized thatrepresents the relation between the amplitude value V_(SW) and theamount of the phase shift in the phase adjuster unit 29.

Modification Example 2-2

In the forgoing embodiment, the amount of the phase shift in the phaseadjuster unit 29 is set on the basis of the amplitude value V_(SW).However, this is non-limiting. In the following, this modificationexample is described in detail by giving some examples.

FIG. 13 illustrates one configuration example of a communication system2B according to this modification example. The communication system 2Bincludes a communication device 40B. The communication device 40Bincludes the demodulator unit 27B and a communication controller unit42B. The demodulator unit 27B performs the demodulating operation on thebasis of the voltage signal at the other end of the coil 21, to receivethe data D1 transmitted from the communication device 10, whiledistinguishing the standard with which the communication device 10 is inconformity (the communication standard SP). The communication controllerunit 42B sets the amount of the phase shift in the phase adjuster unit29 on the basis of the communication standard SP.

Here, the phase adjuster unit 29, the demodulator unit 27B, and thecommunication controller unit 42B correspond to one specific example ofthe “phase adjuster” in the disclosure.

FIG. 14 illustrates one operation example of the communication system2B.

First, as with the case of the communication system 2 (FIG. 11), thecommunication device 10 transmits, by the ASK modulation, the data D1 tothe communication device 40B (step S1). The demodulator unit 27B of thecommunication device 40B makes the confirmation as to whether or not thedemodulator unit 27B has received the data D1 (step S2).

Thereafter, the demodulator unit 27B of the communication device 40Bdistinguishes the communication standard SP (step S13).

Thereafter, the communication controller unit 42B of the communicationdevice BOB sets the amount of the phase shift in the phase adjuster unit29 on the basis of the communication standard SP distinguished in stepS13 (step S54).

Thereafter, the communication device 40B transmits, by the active loadmodulation, the data D2 to the communication device 10 (step S37).

Thus, the flow ends.

As described, in the communication system 2B, the amount of the phaseshift in the phase adjuster unit 29 is set on the basis of thecommunication standard SP. Hence, it is possible to enhance a degree offreedom in setting the amount of the phase shift. Specifically, forexample, in a case where the communication standard SP is a standardutilized in the applications with the long communication distances, itis possible to set the amount of the phase shift, so as to increase thecommunication-enabling distance even more. As a result, in thecommunication system 2B, it is possible to enhance the communicationquality.

FIG. 15 illustrates one configuration example of another communicationsystem 2C according to this modification example. The communicationsystem 2C includes a communication device 40C. The communication device40C includes the demodulator unit 27B and a communication controllerunit 42C. The communication controller unit 42C sets the amount of thephase shift in the phase adjuster unit 29 on the basis of thecommunication standard SP and on the basis of the amplitude valueV_(SW). Specifically, the communication controller unit 42C makes achange-over of the predetermined threshold value Vth2 and a change-overof the amounts of the phase shift P1 and P2, on the basis of thecommunication standard SP.

Here, the phase adjuster unit 29, the amplitude detector unit 30, thedemodulator unit 27B, and the communication controller unit 42Ccorrespond to one specific example of the “phase adjuster” in thedisclosure.

FIG. 16 illustrates one operation example of the communication system2C.

First, as with the case of the communication system 2B (FIG. 14), thecommunication device 10 transmits, by the ASK modulation, the data D1 tothe communication device 40C (step S1). The demodulator unit 27B of thecommunication device 40C makes the confirmation as to whether or not thedemodulator unit 27B has received the data D1 (step S2).

Thereafter, the demodulator unit 27B of the communication device 40Cdistinguishes the communication standard SP (step S13).

Thereafter, the communication controller unit 42C of the communicationdevice 40C sets the threshold value Vth2, and the amounts of the phaseshift P1 and P2, on the basis of the communication standard SPdistinguished in step S13 (step S64).

Thereafter, the amplitude detector unit 30 of the communication device40C detects the amplitude value V_(SW) of the voltage signal at theother end of the coil 21 (step S3).

Thereafter, the communication controller unit 42C of the communicationdevice 40C compares the amplitude value V_(SW) detected in step S3 withthe predetermined threshold value Vth2 (step S34). In a case where theamplitude value V_(SW) is equal to or larger than the threshold valueVth2 (V_(SW)≧Vth2), the communication controller unit 42C sets theamount of the phase shift in the phase adjuster unit 29 at the amount ofthe phase shift P1 (step S35). Meanwhile, in a case where the amplitudevalue V_(SW) is smaller than the threshold value Vth2 (V_(SW)<Vth2), thecommunication controller unit 42C sets the amount of the phase shift inthe phase adjuster unit 29 at the amount of the phase shift P2 (stepS36).

Thereafter, the communication device 40C transmits, by the active loadmodulation, the data D2 to the communication device 10 (step S37).

Thus, the flow ends.

As described, in the communication system 2C, the change-over of thethreshold value Vth2 and the change-over of the amounts of the phaseshift P1 and P2 are made on the basis of the communication standard SP.Hence, it is possible to enhance the degree of the freedom in settingthe amount of the phase shift. As a result, in the communication system2C, it is possible to enhance the communication quality.

3. Third Embodiment

Description is given next of a communication system 3 according to athird embodiment. In this embodiment, a configuration is made to be ableto select either the passive load modulation or the active loadmodulation. In addition, this embodiment includes setting the amount ofthe phase shift in the phase adjuster unit 29, in a case where theactive load modulation has been selected. It is to be noted thatsubstantially same constituent parts as those of the communicationsystems 1 and 2 according to the first and second embodiments aredenoted by the same reference characters, and description thereof isomitted as appropriate.

FIG. 17 illustrates one configuration example of the communicationsystem 3 according to this embodiment. The communication system 3includes a communication device 50. The communication device 50 includesa communication controller unit 52. The communication controller unit 52generates the switch control signals SW1 and SW2 on the basis of thecommunication standard SP and on the basis of the data D2. Specifically,as with the communication controller unit 32B according to themodification example of the first embodiment, the communicationcontroller unit 52 turns on and off the switches 23A and 23B inaccordance with the data D2, in the case where the communicationstandard SP is included in the one or more communication standards setin advance. In other words, in this case, the communication device 50utilizes the active load modulation. Moreover, the communicationcontroller unit 52 turns on and off the switch 25 in accordance with thedata D2, in the case where the communication standard SP is not includedin the one or more communication standards. In other words, in thiscase, the communication device 50 utilizes the passive load modulation.At this occasion, in utilizing the active load modulation, thecommunication controller unit 52 also has a function of controlling theamount of the phase shift in the phase adjuster unit 29, on the basis ofthe amplitude value V_(SW), as with the communication controller unit 42according to the second embodiment.

FIG. 18 illustrates one operation example of the communication system 3.

First, as with the case of the communication system 1B according to themodification example of the first embodiment (FIG. 6), the communicationdevice 10 transmits, by the ASK modulation, the data D1 to thecommunication device 50 (step S1). The demodulator unit 27B of thecommunication device 50 makes the confirmation as to whether or not thedemodulator unit 27B has received the data D1 (step S2).

Thereafter, the demodulator unit 27B of the communication device 50distinguishes the communication standard SP (step S13).

Thereafter, the communication controller unit 32B of the communicationdevice 50 makes the confirmation as to whether or not the communicationstandard. SP distinguished in step S13 is included in the one or morepredetermined communication standards set in advance (step S14). In thecase where the communication standard SP is not included in the one ormore predetermined communication standards, the communication device 50transmits, by the passive load modulation, the data D2 to thecommunication device 10 (step S16).

In step S14, in the case where the communication standard SP is includedin the one or more predetermined communication standards, the amplitudedetector unit 30 of the communication device 50 detects the amplitudevalue V_(SW) of the voltage signal at the other end of the coil 21 (stepS3).

Thereafter, the communication controller unit 52 of the communicationdevice 50 compares the amplitude value V_(SW) detected in step S3 withthe predetermined threshold value Vth2 (step S34). In the case where theamplitude value V_(SW) is equal to or larger than the threshold valueVth2 (V_(SW)≧Vth2), the communication controller unit 52 sets the amountof the phase shift in the phase adjuster unit 29 at the amount of thephase shift P1 (step S35). Meanwhile, in the case where the amplitudevalue V_(SW) is smaller than the threshold value Vth2 (V_(SW)<Vth2), thecommunication controller unit 52 sets the amount of the phase shift inthe phase adjuster unit 29 at the amount of the phase shift P2 (stepS36).

Thereafter, the communication device 50 transmits, by the active loadmodulation, the data D2 to the communication device 10 (step S37).

Thus, the flow ends.

As described, in this embodiment, the configuration is made to be ableto select either the passive load modulation or the active loadmodulation. In addition, this embodiment includes adjusting the amountof the phase shift in the phase adjuster unit 29 in the case where theactive load modulation has been selected. Hence, it is possible toenhance the communication quality.

Although description has been made by giving the embodiments and themodification examples, the contents of the technology are not limited tothe above-mentioned example embodiments and may be modified in a varietyof ways.

For example, the third embodiment provides a combination of thecommunication controller unit 32B according to the modification exampleof the first embodiment and the communication controller unit 42according to the second embodiment. However, this is non-limiting. Theremay be provided any combinations of the communication controller unitsaccording to the embodiments and their modification examples.

It is to be noted that effects described herein are merely exemplified.Effects of the disclosure are not limited to the effects describedherein. Effects of the disclosure may further include other effects thanthe effects described herein.

Moreover, for example, the technology may have the followingconfiguration.

(1) A communication device, including:

a signal generator that generates, on the basis of a first signalreceived from a communication partner through a coil, a second signalthat synchronizes with the first signal;

a first modulator configured to be able to modulate the first signal onthe basis of the second signal;

a second modulator configured to be able to modulate the first signal;and

a communication controller that selects, on the basis of the firstsignal, whichever modulator is to be operated, from the first modulatorand the second modulator.

(2) The communication device according to (1), in which thecommunication controller selects, on the basis of an amplitude value ofthe first signal, whichever modulator is to be operated, from the firstmodulator and the second modulator.

(3) The communication device according to (2), in which thecommunication controller selects the second modulator on the conditionthat the amplitude value is larger than a predetermined value, andselects the first modulator on the condition that the amplitude value issmaller than the predetermined value.

(4) The communication device according to (3), in which

the communication controller sets the predetermined value on the basisof a communication method with the communication partner.

(5) The communication device according to (1), in which thecommunication controller selects, on the basis of a communication methodwith the communication partner, whichever modulator is to be operated,from the first modulator and the second modulator.

(6) The communication device according to (4) or (5), in which

the communication partner modulates the first signal, and

the communication controller distinguishes the communication method onthe basis of a degree of modulation of the first signal modulated by thecommunication partner.

(7) The communication device according to any one of (1) to (6), furtherincluding a phase adjuster that adjusts a phase of the second signal onthe basis of the first signal, in which

the first modulator is configured to be able to modulate the firstsignal on the basis of the second signal the phase of which has beenadjusted by the phase adjuster.

(8) The communication device according to any one of to (7), in which

the signal generator includes a phase synchronization circuit.

(9) The communication device according to any one of to (8), in which

the first modulator includes a first switch, and turning on of the firstswitch causes the second signal to be supplied to the coil.

(10) The communication device according to any one of (1) to (9), inwhich

the second modulator includes a second switch coupled to the coil.

(11) A communication device, including:

a signal generator that generates, on the basis of a first signalreceived from a communication partner through a coil, a second signalthat synchronizes with the first signal;

a phase adjuster that adjusts a phase of the second signal on the basisof the first signal; and

a first modulator configured to be able to modulate the first signal onthe basis of the second signal the phase of which has been adjusted bythe phase adjuster.

(12) The communication device according to (11), in which

the phase adjuster adjusts the phase of the second signal on the basisof an amplitude value of the first signal.

(13) The communication device according to (12), in which

the phase adjuster sets the phase of the second signal at a first phasevalue on the condition that the amplitude value is larger than apredetermined value, and sets the phase of the second signal at a secondphase value on the condition that the amplitude value is smaller thanthe predetermined value.

(14) The communication device according to (13), in which

the phase adjuster sets the predetermined value on the basis of acommunication method with the communication partner.

(15) The communication device according to (14), in which

the phase adjuster sets the first phase value and the second phase valueon the basis of the communication method with the communication partner.

(16) The communication device according to (11), in which

the phase adjuster adjusts the phase of the second signal on the basisof a communication method with the communication partner.

(17) The communication device according to any one of (14) to (16), inwhich

the communication partner modulates the first signal, and

the phase adjuster distinguishes the communication method on the basisof a degree of modulation of the first signal modulated by thecommunication partner.

(18) The communication device according to any one of (11) to (17),further including:

a second modulator configured to be able to modulate the first signal;and

a communication controller that selects, on the basis of the firstsignal, whichever modulator is to be operated, from the first modulatorand the second modulator, in which

the phase adjuster adjusts the phase of the second signal on the basisof the first signal, on the condition that the communication controllerhas selected the first modulator.

(19) A communication method, including:

allowing a coil to receive a first signal from a communication partner;

generating, on the basis of the first signal, a second signal thatsynchronizes with the first signal; and

selecting, on the basis of the first signal, whichever modulator is tobe operated, from a first modulator and a second modulator, the firstmodulator being configured to be able to modulate the first signal onthe basis of the second signal, and the second modulator beingconfigured to be able to modulate the first signal.

(20) A communication method, including:

allowing a coil to receive a first signal from a communication partner;

generating, on the basis of the first signal, a second signal thatsynchronizes with the first signal;

adjusting a phase of the second signal on the basis of the first signal;and

allowing a first modulator to operate, the first modulator beingconfigured to be able to modulate the first signal on the basis of thesecond signal the phase of which has been adjusted.

This application claims the benefit of Japanese Priority PatentApplication JP2015-53573 filed on Mar. 17, 2015, the entire contents ofwhich are incorporated herein by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A communication device, comprising: a signal generator thatgenerates, on a basis of a first signal received from a communicationpartner through a coil, a second signal that synchronizes with the firstsignal; a first modulator configured to be able to modulate the firstsignal on a basis of the second signal; a second modulator configured tobe able to modulate the first signal; and a communication controllerthat selects, on the basis of the first signal, whichever modulator isto be operated, from the first modulator and the second modulator. 2.The communication device according to claim 1, wherein the communicationcontroller selects, on a basis of an amplitude value of the firstsignal, whichever modulator is to be operated, from the first modulatorand the second modulator.
 3. The communication device according to claim2, wherein the communication controller selects the second modulator ona condition that the amplitude value is larger than a predeterminedvalue, and selects the first modulator on a condition that the amplitudevalue is smaller than the predetermined value.
 4. The communicationdevice according to claim 3, wherein the communication controller setsthe predetermined value on a basis of a communication method with thecommunication partner.
 5. The communication device according to claim 1,wherein the communication controller selects, on a basis of acommunication method with the communication partner, whichever modulatoris to be operated, from the first modulator and the second modulator. 6.The communication device according to claim 4, wherein the communicationpartner modulates the first signal, and the communication controllerdistinguishes the communication method on a basis of a degree ofmodulation of the first signal modulated by the communication partner.7. The communication device according to claim 1, further comprising aphase adjuster that adjusts a phase of the second signal on the basis ofthe first signal, wherein the first modulator is configured to be ableto modulate the first signal on the basis of the second signal the phaseof which has been adjusted by the phase adjuster.
 8. The communicationdevice according to claim 1, wherein the signal generator includes aphase synchronization circuit.
 9. The communication device according toclaim 1, wherein the first modulator includes a first switch, andturning on of the first switch causes the second signal to be suppliedto the coil.
 10. The communication device according to claim 1, whereinthe second modulator includes a second switch coupled to the coil.
 11. Acommunication device, comprising: a signal generator that generates, ona basis of a first signal received from a communication partner througha coil, a second signal that synchronizes with the first signal; a phaseadjuster that adjusts a phase of the second signal on the basis of thefirst signal; and a first modulator configured to be able to modulatethe first signal on a basis of the second signal the phase of which hasbeen adjusted by the phase adjuster.
 12. The communication deviceaccording to claim 11, wherein the phase adjuster adjusts the phase ofthe second signal on a basis of an amplitude value of the first signal.13. The communication device according to claim 12, wherein the phaseadjuster sets the phase of the second signal at a first phase value on acondition that the amplitude value is larger than a predetermined value,and sets the phase of the second signal at a second phase value on acondition that the amplitude value is smaller than the predeterminedvalue.
 14. The communication device according to claim 13, wherein thephase adjuster sets the predetermined value on a basis of acommunication method with the communication partner.
 15. Thecommunication device according to claim 14, wherein the phase adjustersets the first phase value and the second phase value on the basis ofthe communication method with the communication partner.
 16. Thecommunication device according to claim 11, wherein the phase adjusteradjusts the phase of the second signal on a basis of a communicationmethod with the communication partner.
 17. The communication deviceaccording to claim 14, wherein the communication partner modulates thefirst signal, and the phase adjuster distinguishes the communicationmethod on a basis of a degree of modulation of the first signalmodulated by the communication partner.
 18. The communication deviceaccording to claim 11, further comprising: a second modulator configuredto be able to modulate the first signal; and a communication controllerthat selects, on the basis of the first signal, whichever modulator isto be operated, from the first modulator and the second modulator,wherein the phase adjuster adjusts the phase of the second signal on thebasis of the first signal, on a condition that the communicationcontroller has selected the first modulator.
 19. A communication method,comprising: allowing a coil to receive a first signal from acommunication partner; generating, on a basis of the first signal, asecond signal that synchronizes with the first signal; and selecting, onthe basis of the first signal, whichever modulator is to be operated,from a first modulator and a second modulator, the first modulator beingconfigured to be able to modulate the first signal on a basis of thesecond signal, and the second modulator being configured to be able tomodulate the first signal.
 20. A communication method, comprising:allowing a coil to receive a first signal from a communication partner;generating, on a basis of the first signal, a second signal thatsynchronizes with the first signal; adjusting a phase of the secondsignal on a basis of the first signal; and allowing a first modulator tooperate, the first modulator being configured to be able to modulate thefirst signal on a basis of the second signal the phase of which has beenadjusted.